Engineered building materials are gaining acceptance in commercial and residential construction. Flooring elements in the form of flooring strips, planks and panels are increasingly being made of engineered materials. For example, engineered flooring elements such as those described above may be of a laminate construction comprising an engineered substrate with a veneer overlying the substrate. The veneer can provide the appearance of a solid wood flooring element or can provide any other design. The veneer may be of wood or another material.
The engineered substrate to which the veneer is laminated may be of a variety of different materials. Two representative examples of engineered materials utilized as a flooring element substrate are medium-density fiberboard (MDF) and high-density fiberboard (HDF). MDF is a generic term which refers to engineered wood products made of wood fibers combined with a binder system and formed under high pressure and temperature into panels. HDF is a generic term which refers to engineered wood products which are denser and stronger than MDF. HDF material may be made of highly compressed exploded wood fibers and resin to yield the dense finished product after high temperature and pressure forming.
The density of MDF is typically between about 31 to 62 lbs/ft3 with the actual density being influenced by the density of the fiber used to manufacture the MDF panel. HDF density is typically between about 50 to about 65 lbs/ft3 or greater.
Engineered flooring elements are frequently manufactured to have an interlocking or “snap fit” connection between adjacent flooring elements. The connection is provided at a joint formed by a male tongue and a female groove on opposite sides of the substrate portion of the flooring element. The male and female tongue-and-groove elements are keyed to fit together and to provide the interlocking connection.
The engineered flooring elements including a laminate of a veneer and a dense substrate tend to be relatively thin, generally having a thickness ranging from 0.312 inch to 0.625 inch. Such thickness is less than a typical natural hardwood flooring element which is generally about 0.750 inch thick. Flooring elements are provided in a variety of widths with flooring elements having a width of about 5 inches or greater being referred to as “planks” while flooring elements with a width of 5 inches or less are typically referred to as “strips.” Engineered flooring element planks and strips are offered in the above-mentioned thickness range.
Flooring elements are most typically arranged on, and are secured to, a subfloor. A subfloor is a planar surface typically consisting of plywood or the like. It is highly preferred that the flooring elements are secured to the subfloor by mechanical fasteners such as cleats, nails or staples. Mechanical fasteners are preferred because such fasteners can be driven very quickly and easily using a fastener-driving tool. An entire flooring element can be secured to the subfloor in seconds using mechanical fasteners. Mechanical fasteners are also desirable because they are economical and have no negative environmental impact.
In a “blind” fastening process, a mechanical fastener is driven at an angle into a side surface of the flooring element. The fastener is completely hidden from view when the adjacent flooring element is fitted against the secured flooring element This leaves only the top surface of the flooring element viewable after the installation. In a “surface” fastening process (i.e., face nailing), the mechanical fastener is driven through the top surface of the flooring element and into the subfloor. The driven end of the fastener can be on the surface of the flooring element or can be countersunk into the flooring element.
A disadvantage of engineered flooring element materials, particularly those including a laminate of a veneer over a dense substrate portion, is that it is difficult to drive a mechanical fastener into and through the flooring element. This is because the high density of the flooring element material provides significant resistance to movement of the fastener. The dense substrate portion does not yield easily to the mechanical fastener. In contrast, natural wood receives a mechanical fastener easily because natural wood tends to collapse at the cellular level enabling the mechanical fastener to penetrate the wood. The engineered flooring element material must actually be displaced away from the mechanical fastener because it does not collapse as does the natural wood.
Problems arise when the dense material of the engineered flooring element substrate is displaced away from the mechanical fastener. More specifically, the displaced material forms a raised or protruding blemish around the driven end of the mechanical fastener. In the blind fastening process, these raised blemishes are formed in the side of the flooring element and can interfere with the interconnection of the adjacent flooring elements at the interlocking connection between adjacent flooring elements. This is a particular problem for “snap fit” type flooring elements because the joints are engineered with close tolerances.
In addition, the displaced material can lift the veneer adjacent the mechanical fastener creating a series of bump-type raised protrusions or blemishes in the veneer. These protrusions are very apparent and are considered to be unattractive, rendering the flooring element defective. In the surface nailing process, the material displaced from around the mechanical fastener becomes a raised and undesirable blemish in the veneer which detracts from the appearance of the flooring element.
Still another problem associated with driving a mechanical fastener into a dense engineered flooring element is that the fastener will frequently not penetrate fully into the flooring element because of the high density of the flooring element material. Even relatively thin engineered flooring elements can be very dense making complete fastener driving difficult. Partial driving of the fastener into the flooring element would leave the fastener projecting above the flooring element after driving. A separate labor-intensive countersinking step is required to manually set the fastener fully within the flooring element.
An undesirable solution to partial driving of the fastener into the flooring element is to increase the amount of force used to drive the fastener into the dense engineered flooring element. Mechanical fasteners are frequently driven with a pneumatic fastener-driving tool. If more force is required to drive the mechanical fastener into a dense engineered flooring element, then a corresponding increase in the air pressure used to power the pneumatic fastener-driving tool must be provided. For typical trigger-actuated fastener-driving tools routinely used by the flooring trade, the increase in air pressure required can be as much as 100% greater than the air pressure required to drive a mechanical fastener into natural wood (e.g., 50-60 psi for natural wood as compared with 100 psi for engineered material). Any increase in needed air pressure causes excessive wear on the air compressor unit, air fittings and fastener-driving tool increasing costs to the flooring installer.
Even if sufficient force is applied to drive the fastener, the fastener itself can fail when it is driven into the dense engineered flooring element. For example, the shank and head of the fastener can fatigue and bend when the head contacts the dense substrate material. Put another way, the fastener, rather than the flooring element material, yields when the fastener is driven. Bending of the fastener can cause the fastener and/or the head to protrude above the surface of the flooring element thus requiring the separate and labor-intensive countersinking step or removal of the fastener.
Possibly as a consequence of the aforementioned problems, manufacturers of engineered flooring elements of the types described above recommend that the flooring elements be secured to the subfloor or other surface by means of adhesive. Adhesives, however, are not optimally advantageous because adhesives require an inconvenient and time-consuming application step, require time to cure, are costly, and can be environmentally unfriendly because adhesives can contain, for example, volatile organic compounds. For a flooring installer, time is money and adhesives are less advantageous than mechanical fasteners in most flooring element applications.
As an alternative to adhesive, certain engineered flooring elements can be installed as a “floating” floor. In a floating floor, the flooring material simply rests on a cushion overlying the subfloor. The flooring elements are not mechanically attached to the subfloor. Floating floors, however, are not optimally advantageous because the flooring elements can move and feel less stable and secure when walked upon.
It would be an improvement in the art to provide an improved mechanical fastener which could be used to secure dense engineered building materials, such as flooring elements, to a subfloor or other surface, which would minimize blemish formation around the driven fastener, which would be robust, which would minimize wear on the fastener-driving tools, which would be efficient and economical to use and which would generally improve the installation of dense engineered building materials.